Question

我已经编写了一个SQL查询，它在结果集中返回一个coulmn：

rate此处有float类型。

SELECT rate 
    FROM partner.exchange
    WHERE id in (
     (SELECT max(id) 
    FROM partner.exchange 
    WHERE currency_id = 1), 
     (SELECT max(id) 
    FROM partner.exchange 
    WHERE currency_id = 2), 
     (SELECT max(id) 
    FROM partner.exchange 
    WHERE currency_id = 3)
    );

我需要编写plpgsql函数，将该结果放入float数组并返回一个。我怎么能这样做？

Answer 1

由于查询的结果只有一列，因此可以将其行放入数组：

SELECT ARRAY(SELECT rate FROM ...[rest of subquery]);

要从SQL中获取此数组中的特定元素，比如第3个元素，您可以写：

SELECT s.x[3] FROM 
 (SELECT ARRAY(SELECT rate FROM ...[rest of subquery]) AS x)
 AS s;

在程序风格上，这可能是：

DECLARE
  x float[];
  ...
BEGIN
  ...
  SELECT ARRAY(SELECT rate FROM ...[rest of subquery]) INTO x;
  RETURN x[3];
END

将查询结果放入数组中

1 个答案: